Fifty years ago, on August 2, 1964, the destroyer USS Maddox (above), exchanged fire with three North Vietnamese torpedo boats in the Gulf of Tonkin.

Two days later, the same destroyer fired on radar targets, which in years since, have been disputed as having been actual ships and not radar anomalies. Within minutes, President Lyndon B. Johnson authorized military action.

On August 10, Congress passed a joint resolution giving the president the use of "conventional" military force in Vietnam, effectively becoming the legal rationale for the Vietnam war.

This slideshow is a look back at the conflict in Southeast Asia through photographs.

Secretary of Defense Robert McNamara indicates on a map where U.S. Navy aircraft made strikes at North Vietnamese PT boats and their shore bases in retaliation for the two attacks on American craft in the Gulf of Tonkin at a Pentagon news briefing, Aug. 5, 1964, Washington, D.C.

Secretary of Defense Robert McNamara indicates on a map where U.S. Navy aircraft made strikes at North Vietnamese PT boats and their shore bases in retaliation for the two attacks on American craft in the Gulf ... more

Photo: AP

Secretary of Defense Robert McNamara indicates on a map where U.S.... Photo-6670357.90833 - Beaumont Enterprise

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This photo provided by the US Navy shows a North Vietnamese motor torpedo boat attacking the USS Maddox, Aug. 2, 1964 in the Gulf of Tonkin. A spy-agency analysis released Thursday contends a second attack on the USS Maddox and the C. Turner Joy in the Gulf of Tonkin Aug. 4, 1964 never happened, casting further doubt on the leading rationale for escalation of the Vietnam War. less

This photo provided by the US Navy shows a North Vietnamese motor torpedo boat attacking the USS Maddox, Aug. 2, 1964 in the Gulf of Tonkin. A spy-agency analysis released Thursday contends a second attack on ... more

Photo: Anonymous, ASSOCIATED PRESS

This photo provided by the US Navy shows a North Vietnamese motor... Photo-6670358.90833 - Beaumont Enterprise

The second wave of combat helicopters of the 1st Air Cavalry Division fly over an RTO and his commander on an isolated landing zone during Operation Pershing, a search and destroy mission on the Bong Son Plain and An Lao Valley of South Vietnam, during the Vietnam War, 1967. less

The second wave of combat helicopters of the 1st Air Cavalry Division fly over an RTO and his commander on an isolated landing zone during Operation Pershing, a search and destroy mission on the Bong Son Plain ... more

Photo: Patrick Christain, Getty Images

The second wave of combat helicopters of the 1st Air Cavalry... Photo-6670309.90833 - Beaumont Enterprise

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A US paratrooper of 2nd Battalion, 503rd Airborne Infantry Regiment during Operation Junction City in South Vietnam during war, 1967.

A US paratrooper of 2nd Battalion, 503rd Airborne Infantry Regiment during Operation Junction City in South Vietnam during war, 1967.

Front row, from left to right, Chairman Nguyen Van Thieu, President Lyndon B. Johnson and Prime Minister Nguyen Cao Ky salute during the playing of the American and Vietnamese national anthems at Guam's International Airport, Agana, March 20, 1967. Johnson gathered his top domestic officials with South Vietnamese leaders for a Guam Island conference to discuss the ongoing war in Vietnam. less

Front row, from left to right, Chairman Nguyen Van Thieu, President Lyndon B. Johnson and Prime Minister Nguyen Cao Ky salute during the playing of the American and Vietnamese national anthems at Guam's ... more

A North Vietnamese woman or girl points a rifle at American POW Gerald Santo Venanzi, a first lieutenant in the U.S. Air Force, as he walks in front of her through vegetation during the Vietnam War, North Vietnam, 1967 less

A North Vietnamese woman or girl points a rifle at American POW Gerald Santo Venanzi, a first lieutenant in the U.S. Air Force, as he walks in front of her through vegetation during the Vietnam War, North ... more

Photo: Hulton Archive, Getty Images

A North Vietnamese woman or girl points a rifle at American POW... Photo-6670299.90833 - Beaumont Enterprise

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A South Vietnamese soldier crouched next to badly bleeding woman while awaiting medical aid during an attack by the Viet Cong, 1968.

A South Vietnamese soldier crouched next to badly bleeding woman while awaiting medical aid during an attack by the Viet Cong, 1968.

Martin Luther King Jr. and other members of the Clergy and Laity Concerned About the War in Vietnam (CALCAV) protest the Vietnam War at Arlington National Cemetery. Photographed February 6, 1968 in Arlington, Virginia. less

Martin Luther King Jr. and other members of the Clergy and Laity Concerned About the War in Vietnam (CALCAV) protest the Vietnam War at Arlington National Cemetery. Photographed February 6, 1968 in Arlington, ... more

Photo: Charles Del Vecchio, Washington Post

Martin Luther King Jr. and other members of the Clergy and Laity... Photo-6670332.90833 - Beaumont Enterprise

A group of civilian women and children rounded up to be killed by US Army during massacre of village while in pursuit of Vietcong militia, as per order of Lieut. William Calley Jr. (later court-martialed), later known as the Vietnam War's Mylai massacre, 1968. less

A group of civilian women and children rounded up to be killed by US Army during massacre of village while in pursuit of Vietcong militia, as per order of Lieut. William Calley Jr. (later court-martialed), ... more

Photo: Ronald S. Haeberle, Time & Life Pictures/Getty Image

A group of civilian women and children rounded up to be killed by... Photo-6670319.90833 - Beaumont Enterprise

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Taboola Gallery Frame Item-85307.90833 - Beaumont Enterprise

Image 36 of 62

US troops take cover from the Vietcong in a trench on Hill Timothy, during the Vietnam War, 1968.

US troops take cover from the Vietcong in a trench on Hill Timothy, during the Vietnam War, 1968.

Photo: Terry Fincher, Getty Images

US troops take cover from the Vietcong in a trench on Hill Timothy,... Photo-6670298.90833 - Beaumont Enterprise

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War photographers Terry Fincher of the Daily Express, left, and Larry Burrows from Life Magazine, right, on Hill Timothy, Vietnam, 1968.

War photographers Terry Fincher of the Daily Express, left, and Larry Burrows from Life Magazine, right, on Hill Timothy, Vietnam, 1968.

Young men raise their fists and chant slogans during the 'Days of Rage' demonstrations organized by the Weathermen to protest the Chicago Seven trial and 'to bring the war home,' Chicago, October 11, 1969. The plinth in the background held a statue dedicated to the policemen killed during the Haymarket Riot until the Weathermen bombed it on October 8th. It was rebuilt and bombed again in 1970 then rebuilt and moved indoors to the police academy. less

Young men raise their fists and chant slogans during the 'Days of Rage' demonstrations organized by the Weathermen to protest the Chicago Seven trial and 'to bring the war home,' Chicago, October 11, 1969. The ... more

Photo: David Fenton, Getty Images

Young men raise their fists and chant slogans during the 'Days... Photo-6670329.90833 - Beaumont Enterprise

Image 44 of 62

John Lennon and Yoko Ono pose on the steps of the Apple building in London, holding one of the posters that they distributed to the world's major cities as part of a peace campaign protesting against the Vietnam War. 'War Is Over, If You Want It,' 1969. less

John Lennon and Yoko Ono pose on the steps of the Apple building in London, holding one of the posters that they distributed to the world's major cities as part of a peace campaign protesting against the ... more

Photo: Frank Barratt, Getty Images

John Lennon and Yoko Ono pose on the steps of the Apple building in... Photo-6670293.90833 - Beaumont Enterprise

Image 45 of 62

Taboola Gallery Frame Item-85307.90833 - Beaumont Enterprise

Image 46 of 62

American political and social activist Abbie Hoffman speaks from behind a bank of microphones at a rally against the war in Vietnam.

American political and social activist Abbie Hoffman speaks from behind a bank of microphones at a rally against the war in Vietnam.

Photo: David Fenton, Getty Images

American political and social activist Abbie Hoffman speaks from... Photo-6670331.90833 - Beaumont Enterprise

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0-year old paraplegic Lau Nguyen, wounded during the Vietnam War returning home after 3 years of medical treatment in the US, 1970.

0-year old paraplegic Lau Nguyen, wounded during the Vietnam War returning home after 3 years of medical treatment in the US, 1970.

A group of Vietnamese refugees in 1970. Photo-6670297.90833 - Beaumont Enterprise

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A US Marine carries an elderly Vietnamese woman to a helicopter for evacuation to a refugee centre in a combat zone during the Vietnan War, 1970.

A US Marine carries an elderly Vietnamese woman to a helicopter for evacuation to a refugee centre in a combat zone during the Vietnan War, 1970.

Photo: Keystone, Getty Images

A US Marine carries an elderly Vietnamese woman to a helicopter for... Photo-6670294.90833 - Beaumont Enterprise

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Taboola Gallery Frame Item-85307.90833 - Beaumont Enterprise

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American anti-Vietnam War demonstrators in the Reflection Pool in Washington D.C., 1970.

American anti-Vietnam War demonstrators in the Reflection Pool in Washington D.C., 1970.

Photo: Rolls Press/Popperfoto, Popperfoto/Getty Images

American anti-Vietnam War demonstrators in the Reflection Pool in... Photo-6670351.90833 - Beaumont Enterprise

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A U.S. Air Force plane spraying delta area with Agent Orange during Vietnam war, 1970.

A U.S. Air Force plane spraying delta area with Agent Orange during Vietnam war, 1970.

Photo: Dick Swanson, The LIFE Images Collection/Getty

A U.S. Air Force plane spraying delta area with Agent Orange during... Photo-6670317.90833 - Beaumont Enterprise

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Heavyweight boxing champion Muhammad Ali walks through the streets with members of the Black Panther Party, New York, September 1970. Ali was sentenced to five years in prison and his championship title revoked after he was convicted of draft evasion upon his refusal to serve with the American army in Vietnam upon grounds of conscientious objection. The decision was overtuned in 1971. less

Heavyweight boxing champion Muhammad Ali walks through the streets with members of the Black Panther Party, New York, September 1970. Ali was sentenced to five years in prison and his championship title revoked ... more

U.S. president Richard Nixon briefs the leadership of the U.S. Congress before his televised announcement of the ceasefire in the Vietnam War, 1973.

U.S. president Richard Nixon briefs the leadership of the U.S. Congress before his televised announcement of the ceasefire in the Vietnam War, 1973.

Photo: Hulton Archive, Getty Images

U.S. president Richard Nixon briefs the leadership of the U.S.... Photo-6670314.90833 - Beaumont Enterprise

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Taboola Gallery Frame Item-85307.90833 - Beaumont Enterprise

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United States Secretary of State William P. Rogers signing the Vietnam peace treaty in Paris, January 27, 1973.

United States Secretary of State William P. Rogers signing the Vietnam peace treaty in Paris, January 27, 1973.

Photo: Keystone, Getty Images

United States Secretary of State William P. Rogers signing the... Photo-6670287.90833 - Beaumont Enterprise

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Henry Kissinger, US President Nixon's advisor on national security affairs, signs 13 June 1973 in Paris a cease-fire agreement bringing the Vietnam war to an end. The war ended 31 April 1975 when Saigon surrendered almost without fighting to the Viet-cong communist forces, ending the US's 15-year involvement in Vietnam less

Henry Kissinger, US President Nixon's advisor on national security affairs, signs 13 June 1973 in Paris a cease-fire agreement bringing the Vietnam war to an end. The war ended 31 April 1975 when Saigon ... more

Fleeing Americans board a U.S. Marine helicopter at Tan Son Nhut Airbase in Saigon April 1975. American involvement in the Vietnam War came to an end when troops from communist North Vietnam invaded Saigon, the capital of the Republic of Vietnam in the South., 1975. less

Fleeing Americans board a U.S. Marine helicopter at Tan Son Nhut Airbase in Saigon April 1975. American involvement in the Vietnam War came to an end when troops from communist North Vietnam invaded Saigon, the ... more